1. Field of the Invention
This invention relates to a disc having a lead-in region in which table-of-contents data indicating a recording position for a data region are subcoded and recorded, and to a disc recording apparatus and a disc reproducing apparatus employing the disc as a recording medium.
2. Related Art
In a disc apparatus, such as a CD player, adapted for reproducing a compact disc (CD) having concentric tracks on which digital audio data are recorded as a row of pits, a laser beam is irradiated along each track on the disc, as the disc is rotationally driven by a spindle motor at a constant linear velocity (CLV). The digital audio data are reproduced by detecting changes in intensity of the reflected light caused by the presence or absence of pits.
With the above compact disc (CD), a data format is prescribed (standardized), in which each frame is made of a 24-bit synchronizing signals, in the form of Eight-to-Fourteen Modulated data (EFM data) in which 8-bit-per-symbol data are converted into 14 bits or 1 channel bit, 14 bit-per-symbol subcode; 14.times.32 bit or 32 symbol data such as play data and parity, and 3 bits each provided between adjacent symbols, making a sum of 588 bits, in which a 98, eight bit frames are a subcode block, as shown in FIG. 9. The absolute address of each subcode block is afforded by Q-channel subcode signals and data per se such as play data are processed with each subcode block as one unit. A lead-in region is provided on the radially inner side of a data region in which play data etc. are recorded. In the lead-in region, a time code showing the starting position of each of songs recorded in the data region, song number of the first and the last songs on the disc and a time code showing the end position of the last song, are subcoded and recorded as a Table of Contents (TOC) data showing recording positions in the data region in the form of subcoded signals in the Q channel.
On the other hand, with a so-called CD-Interactive or CD-I system in which video data, letter data etc. are recorded simultaneously with audio data on the compact disc (CD), seven different recording modes are prescribed (or standardized) as audio data, as shown in FIG. 10.
With the CD-DA mode, with the sound quality level corresponding to the current 16 bit PCM, a straight PCM (straight pulse code modulation) with the sampling frequency of 44.1 kHz and the number of quantization bits equal to 16, is employed. With the A-level stereo mode and the A-level monaural mode, with the sound quality equivalent to a long-playing record, an adaptive PCM or ADPCM with the sampling frequency of 37.8 kHz and the number of quantization bits equal to 8 is employed. With the B-level stereo mode and the B-level monaural mode, having the sound quality equivalent to FM broadcasting, an ADPCM with the sampling frequency of 37.8 kHz and the number of quantization equal to 4, is employed. Finally, with the C-level stereo mode and the C-level monaural mode, with the sound quality equivalent to AN broadcasting, an ADPCM with the sampling frequency of 18.9 kHz and the number of quantization bits equal to 4, is employed.
Thus, referring to FIG. 10, the bit reduction rate in the A-level stereo mode as compared to the CD-DA mode is 1/2, data are recorded at every two sectors and the playback time per disc is about two hours, the hatched square marks representing sectors where data are not recorded. In the A-level monaural mode, as compared to the cd-DA mode the bit reduction rate is 1/4, data are recorded at every four sectors and the playback time is about four hours. With the B-level stereo mode, as compared to the CD-DA mode, the bit reduction rate is 1/4, data are recorded at every eight sectors and the playback time is about eight hours. With the C-level stereo mode, as compared to the CD-DA mode, the bit reduction rate is 1/18, data are recorded at every 16 sectors and the playback time is about 16 hours.
Recently, a small-sized disc, such as a so-called CD-signal, has been presented to the market, and the tendency is towards further decreasing the disc size.
With the small-sized disc, a space for printing or recording tune data necessary for a user to identify the disc record contents, or so-called label area becomes smaller so that it becomes impossible to write a large number of letters. On the other hand, the letters written in the label area need to be reduced in size and hence become hardly legible.